Fractionation trays are widely used in the petrochemical and petroleum refining industries to promote the multistage vapor-liquid contacting performed in fractionation columns. The normal configuration of a fractionation column includes about 10 to 120 individual trays. Normally the structure of each tray in the column is the same. The trays are mounted horizontally at uniform vertical distances referred to as the tray spacing of the column. This distance may vary within different parts of the column but is normally considered constant. The trays are supported by a ring welded or bolted to the inner surface of the column. From time to time it is necessary or desired to change the number and or type of trays employed in the column, which may in turn, lead to a need to move the support rings to different elevations.